JP2006337835A - Projection-type video display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the color purity of a projected video on a screen from deteriorating, accompanying temperature changes. <P>SOLUTION: Light beams R, G and B being elliptically polarized light from LED light sources 1R, 1G and 1B become parallel beams, respectively, by incident side light pipes 2R, 2G and 2B, and further become light beams R, G and B being S polarized light by polarized light changing elements 3R, 3G and 3B. The light beams R, G and B being the S polarized light, respectively, pass through emitting side light pipes 4R, 4G and 4B and are made incident on dichroic cut filters 5R, 5G and 5B, thereby cutting their parts getting into other color light band, because the band is shifted due to the temperature change. The light beams R, G and B emitted from the dichroic cut filters 5R, 5G and 5B are changed into R video light, G video light and B video light by incident side polarizing plates 6R, 6G and 6B, transmission type video display elements 7R, 7G and 7B and emitting side polarizing plates 8R, 8G and 8B and composed by a dichroic cross prism 9. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention projects light onto a screen using a light valve element such as a transmissive liquid crystal panel or a reflective video display element, for example, a liquid crystal projector device, a reflective video display projector device, a projection display device, etc. The present invention relates to a projection type image display apparatus.

  As a conventional example of a projection-type image display device, an illumination optical system is provided for each of R (blue), G (green), and B (blue) light, and these R, G, and B image lights are synthesized by a dichroic prism. A projection-type image display device that projects on a screen is known (see, for example, Patent Document 1).

In such a projection-type image display device, in each illumination optical system, colored light is emitted from a plurality of light source units, and this emitted light is converted into colored light having a uniform in-plane light intensity distribution by an array lens (integrator). And dichroic prisms synthesize R, G, and B image light emitted from the light valve of the illumination optical system.
JP 2001-343706 A

  By the way, when an LED light source is used as the light source unit in the projection display apparatus, the spectrum of the light emitted from the LED light source unit is shifted by the temperature shift. For this reason, in the projection-type image display apparatus using such an LED light source, there has been a problem that the color purity of a single color or white color of an image projected on a screen deteriorates with a temperature change.

  An object of the present invention is to provide a projection type image display apparatus that can solve such problems and prevent the color purity of the image on the screen from being deteriorated due to a temperature change.

  In order to achieve the above object, the present invention generates an image light by emitting an LED light source that emits light, an illumination optical system that converts light from the LED light source into predetermined polarized light, and the polarized light. And a projection means for projecting the image light emitted from the image display element onto a screen, wherein the polarized light applied to the image display element is set. A dichroic cut filter for cutting light components outside the predetermined band is provided.

  Further, the present invention is characterized in that a difference between a half-value wavelength of the dichroic cut filter and a peak wavelength of light from the light source unit is approximately ½ of the bandwidth of the light.

In the present invention, the half-value wavelength λ _1/2 of the dichroic filter is
λ _P + W / 2−10 ≦ λ _1/2 ≦ λ _P + W / 2 + 10
Or
λ _P −W / 2−10 ≦ λ _1/2 ≦ λ _P −W / 2 + 10
Where λ _{P is} the peak wavelength of light
W: Bandwidth of the spectral spectrum of light.

  Further, the present invention is characterized in that the dichroic cut filter is an ultraviolet cut filter.

  The dichroic cut filter according to the present invention is characterized in that the half-value wavelength of the dichroic cut filter is set on the short wavelength side of the spectral spectrum band of the light, and cuts the shorter wavelength side than the half-value wavelength of the light. Is.

  The dichroic cut filter according to the present invention is characterized in that a half-value wavelength of the dichroic cut filter is set to a longer wavelength side of a band of a spectrum of the light, and a longer wavelength side than the half-value wavelength of the light is cut. Is.

  Further, in the present invention, the dichroic cut filter has a half-value wavelength set to a short wavelength side and a long wavelength side of the spectral spectrum band of the light, and is less than the half-value wavelength on the short wavelength side of the light. It is a band-pass filter that cuts light on the short wavelength side and on the longer wavelength side than the half-value wavelength on the longer wavelength side of the light.

  The dichroic cut filter according to the present invention is characterized in that a half-value wavelength is set on the shift side of a spectral spectrum band of light emitted from the LED light source depending on temperature.

  The present invention is characterized in that a heat sink having a substantially rectangular parallelepiped shape is provided on the side opposite to the light emitting side of the LED light source.

  In order to achieve the above object, the present invention provides first to third LED light sources that respectively emit R (red) light, G (green) light, and B (blue) light, and the first to third LED light sources. First to third illumination optical systems for converting R, G, B light from each of the LED light sources into predetermined linearly polarized light, and R, G, B light from the first to third illumination optical systems, respectively. Are emitted to generate R video light, G video light, and B video light, and the R video light and G video light from the first to third video display elements, respectively. , A projection-type image display device having projection means for projecting B image light onto a screen, wherein the first and third illumination optical systems respectively change the optical paths of R light and B light. Is provided.

  In the invention, it is preferable that the reflection element changes the optical path by approximately 90 °.

  Further, according to the present invention, the change direction of the optical path of the R light by the reflection element of the first illumination optical system and the polarization direction of the optical path of the B light by the reflection element of the third illumination optical system are opposite to each other. It is characterized by being.

  In the present invention, the first and third illumination optical systems convert R and B light incident from the first and third LED light sources into S-polarized R and B light, respectively. The illumination optical system 2 converts G light incident from the second LED light source into P-polarized G light.

Further, the present invention provides a dichroic cross prism that synthesizes the R video light, G video light, and video light from the first to third video display elements,
The dichroic prism is set so that a transmission region through which the G image light can be transmitted and a reflection region through which the B image light can be reflected partially overlap each other.

  According to the present invention, it is possible to prevent the deterioration of the color purity of the projected image on the screen even if the spectral spectrum band of the light from the LED light source shifts due to the temperature change.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a first embodiment of a projection type image display apparatus according to the present invention, where 1R, 1G, and 1B are LED light sources, 2R, 2G, and 2B are incident side light pipes, and 3R, 3G, and 3B. Is a polarization conversion element, 3Ra, 3Ga, and 3Ba are polarization conversion films, 3Rb, 3Gb, and 3Bb are half-wave retardation plates, 3Rc, 3Gc, and 3Bc are incident surfaces, 3Rd, 3Gd, and 3Bd are reflection films, and 3Re, 3Ge , 3Be are triangular prisms, 3Rf, 3Gf, and 3Bf are exit surfaces, 4R, 4G, and 4B are exit side light pipes, 5R, 5B, and 5G are dichroic cut filters, 6R, 6G, and 6B are entrance side polarizing plates, 7R, 7G and 7B are transmissive image display elements, 8 is an exit side polarizing plate, 9 is a dichroic prism, 9R is an R light reflecting dichroic film, 9B is a B light reflecting dichroic film, and 10 is a projection lens, 1 heat sink 12 is a cooling fan.

  The first embodiment includes an LED light source unit, an illumination optical system, and an image display element for each of R (red), G (green), and B (blue) light. The R, G, B image light is synthesized by a dichroic prism, and the synthesized image light is projected onto a screen by a projection lens. Hereinafter, this first embodiment will be described.

  In FIG. 1, R light is emitted from the LED light source 1R, G light is emitted from the LED light source 1G, and B light is emitted from the LED light source 1B, and each enters the illumination optical system. The R light illumination optical system includes an incident side light pipe 2R formed of a transparent glass material, a polarization conversion element 3R, and an output side light pipe 4R formed of glass. The optical system includes an incident side light pipe 2G formed of glass, a polarization conversion element 3G, and an output side light pipe 4G formed of glass, and the illumination optical system for B light is formed of glass. The incident side light pipe 2B, the polarization conversion element 3B, and the emission side light pipe 4B made of glass are used.

  The incident side light pipes 2R, 2G, and 2B have a divergent shape in which the cross section sequentially expands from the incident surface side toward the emission surface side, and the R light emitted from the LED light source 1R is incident on the R light incident side. The G light incident on the light pipe 2R from an incident surface with a narrow cross section and emitted from the LED light source 1G is incident on the incident light pipe 2G for G light from an incident surface with a narrow cross section, and the LED light source The B light emitted from 1B enters the incident light pipe 2B for B light from an incident surface with a narrow cross section.

  According to Etendue's law that the cross-sectional area of the light source x the solid angle = constant, the light from the light source diffuses, and the cross-sectional area perpendicular to the optical axis of the light beam expands. Such enlargement of the cross-sectional area of light from the light source, that is, diffusion is unnecessary, and in particular, when an LED light source having a large divergence angle is used, the light utilization efficiency is deteriorated. The incident side light pipes 2R, 2G, and 2B are used for reducing the light diffusion angle and increasing the light utilization rate.

  For this purpose, first, the opening of the incident surface of the incident light pipe 2R for R light is made the same as the opening of the exit of the LED light source 1R, and the entrance of the LED light source 1R is in contact with the entrance surface and the exit. By arranging the incident light pipe 2R for R light, the R light emitted from the LED light source 1R is effectively incident on the incident light pipe 2R, and the loss of the R light amount is minimized. To.

  Further, in the incident light pipe 2R for R light, since the incident R light is diverging, the R light is reflected on the side surface, the upper surface, and the bottom surface forming the interface between the glass and air. Here, since the incident-side light pipe 2R has a diverging shape, the side surface, the upper surface, and the bottom surface are inclined so as to be farther away from the optical axis of the R light toward the exit surface side. Due to the difference in refractive index between the material and air, the light component that diverges toward the side surface, top surface, and bottom surface of the incident R light is totally reflected by these side surfaces, top surface, and bottom surface, and is reflected in this way. The divergence angle is reduced. That is, the inclination angles with respect to the optical axis of these side surfaces, top surface, and bottom surface are set so that the R light that diverges on these side surfaces, top surface, and bottom surface is totally reflected. In this way, the total reflection at the entire interface reduces the loss of the R light, and the cross section of the incident side light pipe 2R is wider than the incident surface and the divergence angle is reduced. Parallel R light is emitted.

  The same applies to the incident-side light pipes 2G and 2B, and the G light and B light incident on the incident-side light pipes 2G and 2B have a wider cross section than their incident surfaces and a divergent angle is reduced. It becomes parallel light and is emitted from the incident side light pipes 2G and 2B.

  The R, G, and B lights emitted from the light valves 2R, 2G, and 2B are applied to the polarization conversion elements 3R, 3G, and 3B provided on the emission surface side of the light valves 2R, 2G, and 2B, and the incident surfaces 3Rc, 3Gc. , 3Bc.

  The polarization conversion element 3R is made of a transparent glass material, and includes, for example, a polarization separation film 3Ra, a half-wave retardation plate 3Rb, and a reflection film 3Rd that are inclined by 45 ° with respect to the incident surface 3Rc. They are arranged in order. A triangular prism 3Re is attached to the outside of the reflective film 3Rd. Accordingly, the reflective film 3Rd is also formed in the polarization conversion element 3R to protect the reflective film 3Rd and improve the reflectance. I am trying. The polarization conversion elements 3G and 3B have the same configuration, and the polarization separation films 3Ga and 3Ba, ½ wavelength phase difference plates, for example, tilted by about 45 ° with respect to the incident surfaces 3Gc and 3Bc, respectively. 3Gb, 3Bb and reflective films 3Ge, 3Be are arranged in that order.

  Here, the R light emitted from the incident side light pipe 2R is effectively incident on the polarization conversion element 3R, and in order to minimize the loss of light amount, the emission surface of the incident side light pipe 2R and the polarization conversion element 3R The polarization conversion element 3R is arranged with respect to the incident light pipe 2R for R light so that the openings with the incident surface 3Rc are the same, and the exit surface and the incident surface 3Rc are in contact with each other.

  In the polarization conversion element 3R having such a configuration, the elliptically polarized R light incident from the incident surface 3Rc is separated into S-polarized R light and P-polarized R light by the polarization separation film 3Ra. That is, the S-polarized R light is reflected by the polarization separation film 3Ra and its optical path is changed by approximately 90 °, and the P-polarized R light is transmitted through the polarization separation film 3Ra. Here, the inclination angle of the polarization separation film 3Ra with respect to the optical axis of the incident R light is set so as to increase the separation efficiency of the S and P polarized light of the polarization separation film 3Ra. As described above, the light is made to be substantially parallel light by reducing the divergence angle by the incident light pipe 2R for R light, so that the inclination angle of the polarization separation film 3Ra is set to a predetermined angle with respect to the incident R light. (Here, approximately 45 °), the separation efficiency of the S and P polarized light of the polarization separation film 3Ra is high over the entire cross section of the R light, and the incident R light is efficiently converted to S polarized R light. And P-polarized R light can be separated. The S-polarized R light reflected by the polarization separation film 3Ra is emitted from the emission surface 3Rf of the polarization conversion element 3R.

  The P-polarized R light that has been transmitted through the polarization separation film 3Ra and separated is then supplied to the ½ wavelength phase difference plate 3Rb, and the polarization plane is rotated by ½ wavelength within the frequency band. It is converted into polarized R light. The half-wave retardation plate 3Rb is also set with an inclination angle (approximately 45 ° in this case) with respect to the optical axis of the R light so as to obtain a good polarization rotation characteristic in the P-polarized R light band. Further, since the supplied P-polarized R light is also substantially parallel light, the polarization rotation characteristic is further improved. After the P-polarized light is converted to S-polarized light by the half-wave retardation plate 3Rb, the R light is reflected by the reflective film 3Rd and its optical path is changed by approximately 90 °, and then the emission surface 3Rf of the polarization conversion element 3R. It is emitted from. The reflection film 3Rd is also inclined with respect to the optical axis of the R light (in this case) so that good reflection characteristics can be obtained in the band for the S-polarized R light from the half-wave retardation plate 3Rb. However, since the supplied S-polarized R light is also substantially parallel light, the reflection characteristics are further improved.

  In this way, in the polarization conversion element 3R, the elliptically polarized R light is converted to S polarized R light and emitted from the exit surface 3Rf.

  The same applies to the polarization conversion elements 3G and 3B for G and B light, and elliptically polarized G and B light emitted from the incident-side light pipes 2G and 2B is transmitted from the incident surfaces 3Gc and 3Bc to the polarization conversion elements 3G and 3B. Incident light is emitted, and S-polarized parallel G and B light is emitted from the exit surfaces 3Gf and 3Bf. However, in the polarization conversion element 3B, the light path of the B light is changed by 90 ° by the polarization separation film 3Ba and the reflection film 3Gd. The direction of the changed optical path is the optical path of the R light in the polarization conversion element 3R. This is the opposite of the direction of change. In the polarization conversion element 3G, the incident direction and the emitting direction of the G light are substantially the same.

  The R, G, and B lights emitted from the polarization conversion elements 3R, 3G, and 3B are respectively incident on the exit-side light pipes 4R, 4G, and 4B provided on the exit surfaces 3Rf, 3Gf, and 3Bf. .

  The emission side light pipes 4R, 4G, and 4B are made of a transparent glass material, and have a narrowed shape in which the cross section gradually decreases from the incident surface side toward the emission surface side. The S-polarized R light emitted from the polarization conversion element 3R enters the R-light exit side light pipe 4R from an incident surface having a wide cross section, and the S-polarized G light emitted from the polarization conversion element 3R The S-polarized B light incident on the emission side light pipe 4G for G light from the incident surface having a wide cross section and emitted from the polarization conversion element 3B is applied to the emission side light pipe 4B for B light. The light enters from a wide incident surface.

  Then, in order for the R light from the polarization conversion element 3R to be efficiently incident on the emission side light pipe 4R, the opening on the incident surface of the emission side light pipe 4R is defined as the opening on the emission surface 3Rf of the polarization conversion element 3R. By arranging the exit side light pipe 4R with respect to the polarization conversion element 3R so that the entrance surface and the exit surface 3Rf are in contact with each other, the R light emitted from the polarization conversion element 3R is effectively used. The light loss of the R light is minimized by being incident on the emission side light pipe 4R.

  In addition, in the light-emitting side light pipe 4R for R light, the shape thereof is narrowed, and since the incident R light is substantially parallel light, this R light forms an interface with air. Reflected on the side, top, and bottom. That is, since the exit side light pipe 4R has a narrow shape, the side surface, top surface, and bottom surface thereof are inclined so that the exit surface side is closer to the optical axis of the R light. Since the S-polarized R light from the conversion element 3R is substantially parallel light, the light portion (peripheral light) away from the optical axis is directed toward the side surface, the top surface, and the bottom surface of the emission side light pipe 4R. However, due to the difference in refractive index between the glass material of the emission side light pipe 4R and the air outside thereof, the R light directed toward the side surface, top surface, and bottom surface of the emission side light pipe 4R is totally reflected by these side surfaces, top surface, and bottom surface. The optical path is changed to the optical axis side. In other words, the inclination angles of the side surface, top surface, and bottom surface of the emission side light pipe 4R with respect to the optical axis are set so that the R light is totally reflected at the side surface, top surface, and bottom surface.

  In this way, since the ambient light of the R light is totally reflected to the optical axis side, the cross-sectional area is reduced from the exit surface of the exit side light pipe 4R than the R light incident from the entrance surface. Light is emitted, and the light quantity distribution of the ambient light is improved compared to the case where the emission side light pipe 4R has a rectangular parallelepiped shape. Further, in the polarization conversion element 3R, the corners of the triangular prism 3Re may be chipped. However, due to the above-described effect of the exit-side exit-side light pipe 4R, the amount of light on the peripheral side from the center of the cross-section of the R-light (optical axis side). Since the distribution is increased, even if the corners of the triangular prism 3Re are chipped and the R light is lost, the deterioration of the projected image on the screen due to the loss can be suppressed.

  The illumination optical system has the above-described configuration, and a perspective view thereof is shown in FIG. 2A, a side view thereof is shown in FIG. 2B, and a top view thereof is shown in FIG. However, FIG. 2 shows an illumination optical system for R light as a representative, and it goes without saying that the same applies to illumination optical systems for G and B light.

  In FIG. 2C, as described above, the divergent R light from the LED light source 1R is incident on the incident side light pipe 2R from its incident surface 2Rb, converted into substantially parallel R light, and its emission surface. It is emitted from 2Ra. The substantially parallel R light emitted from the incident-side light pipe 2R enters the polarization conversion element 3R from the incident surface 3Rc, and is converted from elliptically polarized light by the polarization separation film 3Ra, the ½ wavelength phase difference plate 3Rb, and the reflection film 3Rd. It is converted into S-polarized light and emitted from the exit surface 3Rf. The substantially parallel R light of S-polarized light emitted from the polarization conversion element 3R is incident on the light-emitting side light pipe 4R from the incident surface 4Ra, and the cross-section of the S-polarized light is reduced so that the surrounding light is directed in the optical axis direction. R light is emitted from the emission surface 4Rb.

  In the polarization conversion element 3R of the illumination optical system having such a configuration, for example, in FIG. 2A and FIG. 2B, the R light incident on the upper surface 3Rg, the lower surface 3Ri, and the side surface 3Rh causes total reflection. Polishing with 5 or less. Thereby, the diverging light remaining in the incident R light hits the upper surface 3Rg, the lower surface 3Ri, or the side surface 3Rh, but is totally reflected by these and returns to the optical path, so that compared with the case where such polishing is not performed. There is little loss of light quantity, and the efficiency, and thus the brightness of the projected image on the screen can be increased.

  Further, in the polarization conversion element 3R, the ½ wavelength phase difference plate 3Rb is provided on the exit side of the polarization separation film 3Ra. According to this, a ½ wavelength phase difference is provided on the exit surface 3Rf of the polarization conversion element 3R. Since it is not necessary to dispose a plate, there is no deviation on the exit surface 3Rf of the optical path of each polarized light after polarization separation, and the exit side light pipe 4R can be easily bonded to the exit surface 3Rf.

  By the way, the opening of the LED light source 1R and the opening of the transmissive image display element 7R (FIG. 1) are determined. For this purpose, the incident surface 2Rb connected to the LED light source 1R of the incident side light pipe 2R in the illumination optical system. Are substantially the same as the LED light source 1R, the openings of the incident light pipe 2R and the polarization conversion element 3R to be connected are equal, the openings of the polarization conversion element 3R and the emission light pipe 4R to be connected are equal, and the light is emitted. The opening of the exit surface 4Rb of the side light pipe 4R is made substantially equal to the opening of the transmissive image display element 7R.

  For example, if the LED light source 1R has an emission opening width 3 × length 4 mm, the opening of the incident surface 2Rb of the incident side light pipe 2R is equal to this, so that the R light emitted from the LED light source 1R can be captured as much as possible. 3 × 4 mm in length. If the opening of the transmission type image display element 7R is 15 mm wide × 9 mm long, the opening of the light exit surface 4Rb of the light pipe 4R on the light exit side is about 1 mm larger than this, and is 16 × 10 mm wide.

  The opening of the incident surface 4Ra of the emission side light pipe 4R is approximately 2 mm larger than the opening of the emission surface 4Rb, and is 18 × 12 mm wide. The opening of the exit surface 3Rf of the polarization conversion element 3R is equal to the opening of the entrance surface 4Ra of the exit side light pipe 4R and is 18 × 12 mm wide so that the R light is efficiently transmitted from the polarization conversion element 3R to the exit side light pipe 4R. To be able to. In the polarization conversion element 3R, the S-polarized light of the R light reflected and separated by the polarization separation film 3Ra and the P-polarized light transmitted and separated by the polarization separation film 3Ra are converted by the half-wave retardation plate 3Rb. The cross section of the S-polarized light obtained in this way is equal, and therefore the opening of the incident surface 3Rc of the polarization conversion element 3R has a vertical width equal to the vertical width of the output surface 3Rf and a horizontal width of 1 equal to the horizontal width of the output surface 3Rf. / 2 is 9 × 12 mm. Therefore, in order to efficiently transmit the R light from the incident side light pipe 2R to the polarization conversion element 3R, the opening of the emission surface 2Ra of the incident side light pipe 2R is also the same as the opening of the incident surface 3Rc of the polarization conversion element 3R. Equally, 9 × 12 mm.

  The opening of the incident surface 2Rb of the incident side light pipe 2R is 3 × 4 mm as described above. Here, the opening of the exit surface 2Ra of the incident-side light pipe 2R is three times as long as the opening of the incident surface 2Rb of the incident-side light pipe 2R, but as described above, the incident R light light The length of the incident side light pipe 2R is set so that the angle of inclination of the interface with air relative to the axis is totally reflected at the interface. As for the exit side light pipe 4R, the opening of the entrance surface 4Ra is about 2 mm larger than the exit of the exit surface 4Rb and is 18 × 12 mm wide, so that the R light incident thereon is at the interface with air. For total reflection, the length may be shorter than the incident side light pipe 2R.

  In this way, the openings between the components from the LED light source 1R to the exit side light pipe 4R are made equal, and the difference between the opening of the image display element 7 and the opening of the LED light source 1R is reduced by the incident light pipe 2R. As a result, light with a smaller divergence angle can be projected onto the image display device, so that high efficiency and high contrast can be obtained. The smaller the entrance aperture is than the exit aperture, the greater the relaxation efficiency of the light diffusion angle.

  Here, the exit surface 2Ra of the incident side light pipe 2R and the entrance surface 3Rc of the polarization conversion element 3R, and the exit surface 3Rf of the polarization conversion element 3R and the entrance surface 4Ra of the exit side light pipe 4R are bonded together. For bonding, a UV adhesive that is cured by irradiation with ultraviolet rays is used. Thereby, deterioration of the light quantity due to the presence of the interface with air can be prevented, and the brightness of the projection screen can be improved. Also, by bonding, the incident side light pipe 2R and the emission side light pipe 4R, which are difficult to hold because the side surfaces are trapezoidal, can be easily held, and the positional displacement of each component due to vibration or impact does not occur. Therefore, it is possible to prevent deterioration of performance such as the brightness of the projection screen due to vibration or the like.

  Returning to FIG. 1, the R light emitted from the emission side light pipe 4R is transmitted from the incident side polarization plate 6R, the transmission type image display element 7R, and the emission side polarization plate 8R via the R light dichroic cut filter 5R. The G light that is incident on the R image light forming system and exits from the exit-side light pipe 4G passes through the dichroic cut filter 5G for G light, and enters the entrance-side polarizing plate 6G, the transmissive image display element 7G, and the exit side. The B light incident on the G image light forming system composed of the polarizing plate 8G and emitted from the output side light pipe 4B passes through the dichroic cut filter 5B for B light, and enters the incident side polarizing plate 6B and the transmissive image display element. 7B and the B-side image light forming system composed of the exit side polarizing plate 8B.

  The dichroic filter transmits light in a specific wavelength region and attenuates light in other wavelength regions (wavelength regions of other color lights). Accordingly, the dichroic cut filter 5R for R light transmits light in the R wavelength region and attenuates light in other wavelength regions, but is emitted from the LED light source 1R according to changes in the ambient temperature. When the spectrum spectrum band of the R light shifts and a part of this spectrum spectrum deviates from the wavelength region of R and enters the wavelength region of G light, that portion is attenuated (cut). Similarly, the dichroic cut filter 5G for G light transmits light in the G wavelength region and attenuates light in other wavelength regions, and is emitted from the LED light source 1G according to changes in the ambient temperature. When the spectral band of the G light shifts and a part of this spectral spectrum deviates from the G wavelength region, that part is attenuated (cut), and the dichroic cut filter 5B for B Transmits light in the B wavelength region and attenuates light in other wavelength regions. The band of the spectrum of B light emitted from the LED light source 1B changes according to the change in the ambient temperature. When a part of the spectral spectrum deviates from the B wavelength region, that part is attenuated (cut).

  That is, generally, the spectral spectrum band of the light emitted from the LED light source is shifted according to the variation of the ambient temperature. When such a band shift occurs, part of the shifted band enters the band of the spectral spectrum of a different color and becomes light of another color, thereby degrading the color purity of the projection screen. The dichroic cut filters 5R, 5G, and 5B thus cut light components that have entered the spectral bands of other colors.

This will be described with reference to FIG. 3. For example, the spectral spectrum SP of the colored light at the reference ambient temperature of 20 ° C. has the peak wavelength λ _P and the bandwidth W, and the allowable lower limit wavelength of this colored light band is λ _{1. When it is set to / 2} , there is a case where a part thereof is shifted to the spectral spectrum SP ′ having the allowable lower limit wavelength λ _1/2 or less due to a change in temperature. A dichroic cut filter is used in order to cut the component having the allowable lower limit wavelength λ _1/2 or less in the spectral spectrum SP ′. For this purpose, the spectral spectrum DSP of this dichroic filter is set so that the half-value wavelength (wavelength at which the relative transmittance is 50%) is the allowable lower limit wavelength λ _1/2 . Hereinafter, the allowable lower limit wavelength λ _{1/2 is referred} to as a half-value wavelength of the dichroic cut filter.

FIG. 4A shows a half-value wavelength λ of the dichroic cut filter when the spectral spectrum SP at the reference ambient temperature cuts unnecessary partial light by shifting in the short wavelength direction indicated by the arrow B due to temperature change. _In this case, assuming that the peak wavelength (approximately the center wavelength) of this spectrum SP is λ _P and the bandwidth is W, the half-value wavelength λ _1/2 is
λ _P −W / 2−10 ≦ λ _1/2 ≦ λ _P −W / 2 + 10 (1)
Set to The spectral spectrum SP in this case corresponds to the spectral spectrum of the R light and G light emitted from the LED light sources 1R and 1G in the case of the first embodiment. For example, the spectral spectrum of G light is close to the spectral spectrum of B light on the short wavelength side, and when the spectral spectrum of G light is shifted to the short wavelength side due to temperature change, it enters the band of B light. It is necessary to cut the component of G light. By setting the half-value wavelength λ _1/2 of the dichroic cut filter 5G (FIG. 1) as shown in FIG. 4A, the component of this G light spectrum with the half-value wavelength λ _1/2 or less is greatly reduced. Will be attenuated.

FIG. 4B shows a half-value wavelength λ of the dichroic cut filter when the spectral spectrum SP when it is at the reference ambient temperature cuts unnecessary partial light due to a change in temperature in the long wavelength direction indicated by the arrow C. _In this case, assuming that the peak wavelength (approximately the center wavelength) of this spectrum SP is λ _P and the bandwidth is W, the half-value wavelength λ _1/2 is
λ _P + W / 2−10 ≦ λ _1/2 ≦ λ _P + W / 2 + 10 (2)
(However, this W / 2 is ½ times the total bandwidth when the spectral spectrum is the target with respect to the peak λ _P , but when it is asymmetric, the peak Width from λ _P to the edge of the band). In the case of the first embodiment, the spectral spectrum SP in this case corresponds to the spectral spectrum of B light and G light emitted from the LED light sources 1B and 1G. For example, the spectrum of the B light is close to the spectrum of the G light on the long wavelength side, and if the spectrum of the B light is shifted to the long wavelength side due to temperature change, it enters the band of the G light. It is necessary to cut the B light component. By setting the half-value wavelength λ _1/2 of the dichroic cut filter 5B (FIG. 1) as shown in FIG. 4 (b), the component of the spectrum of this B light having the half-value wavelength λ _1/2 or less is greatly increased. Will be attenuated.

Although not shown, the dichroic filter 5G for G light is a band-pass filter having half-value wavelengths λ _1/2 on the long wavelength side and the short wavelength side of the spectrum thereof.

  The bandwidth of the emitted light from the LED light source is usually 40 to 80 nm. Therefore, according to the above formulas (1) and (2), the difference between the half-value wavelength of the dichroic filter and the peak wavelength of the emitted light from the LED light source is in the range of 10 to 30 nm in the narrowest bandwidth, For a wide bandwidth, it is in the range of 30-50 nm.

For example, assuming that the peak wavelength λ _P of the R light from the LED light source 1R for R light is 620 nm and the bandwidth is 60 nm at a normal atmospheric temperature of 20 ° C., R In the dichroic cut filter 5R for light, its half-value wavelength λ _1/2 is set within a range of about 580 nm to 600 nm. Further, assuming that the peak wavelength λ _P of B light from the LED light source 1B for B light is 460 nm and the bandwidth is 60 nm, the dichroic cut filter 5B for B light can be obtained from FIG. 4B and the above equation (2). The half-value wavelength λ _1/2 is set within a range of about 480 nm to 500 nm. The dichroic cut filter 5B also has a function of cutting UV (ultraviolet light) by setting a half-value wavelength λ _{1/2 of} 430 nm on the short wavelength side. When the peak wavelength λ _P of the G light LED light source 1G is 510 nm and the band is 80 nm, the half-value wavelength λ ₁ on the short wavelength side of the dichroic cut filter 5G for G light (that is, the spectral spectrum side of B light). _{/ 2} is in the range of about 460 to 480 nm, and the half-value wavelength λ _1/2 on the long wavelength side (that is, the spectral spectrum side of the R light) is set in the range of about 540 to 560 nm.

In this way, by setting the half-value wavelength λ _1/2 of the dichroic cut filter, it is possible to optimize the amount of light that is cut when shifted by a temperature change. If the half-value wavelength λ _1/2 of the dichroic cut filter is too close to the peak wavelength λ _P , the light amount will be cut too much, and if it is too far, the unnecessary light amount cannot be effectively cut. The color purity of the projection screen will deteriorate.

  Note that the dichroic cut filters 5R, 5G, and 5B have variations in the spectral spectra of the R, G, and B light emitted from the LED light sources 1R, 1G, and 1B due to product variations and changes over time. Unnecessary color light due to such variations. Are cut by the dichroic cut filters 5R, 5G, and 5B, and changes in white and single color purity on the screen due to such variations can be prevented.

  Further, these dichroic cut filters 5R, 5G, and 5B are arranged on the incident side of the incident side polarizing plates 6R, 6G, and 6B, respectively, and light in unnecessary bands is cut, so that these incident side polarizing plates 6R, 6G, and 6B are cut. The thermal load (temperature rise) is also reduced.

  Furthermore, the dichroic cut filters 5R, 5G, 5B may be coated on the incident surface or the exit surface of the input side light pipes 2R, 2G, 2B and the exit side light pipes 4R, 4G, 4B. Thereby, bonding costs and member costs can be cut.

  For the R, G, B light emitted from the dichroic cut filters 5R, 5G, 5B, only the S-polarized light is extracted by the incident side polarizing plates 6R, 6G, 6B, respectively. The transmissive image display element 7G for 7R and G light is irradiated to the transmissive image display element 7B for B light. Here, in the first embodiment, the incident-side polarizing plates 6R, 6G, and 6B and the outgoing-side polarizing plates 8R, 8G, and 8B for the respective colors arranged so as to sandwich the video display elements 7R, 7G, and 7B are used. Ensure contrast performance.

  The transmissive video display elements 7R, 7G, and 7B are provided with a liquid crystal display unit having the number of pixels (for example, horizontal 1024 pixels × vertical 768 pixels) corresponding to the pixels to be displayed. Then, each pixel of the liquid crystal display unit is driven by a driving signal based on an image for each color light from the outside, so that the polarization angle of the color light passing through the pixel changes, and the color light in a predetermined polarization direction is emitted on the emission side polarizing plate 8R. , 8G, 8B. That is, in the output side polarizing plates 8R, 8G, and 8B, the transmittance of the colored light changes according to the polarization angle. As a result, the output side polarizing plates 8R, 8G, and 8B change the pixel of the liquid crystal display unit. R, G, and B light of a light amount corresponding to the drive signal (image pixel information) is emitted every time. These R, G, and B lights are R video light, G video light, and B video light including the contents of the R video, G video, and B video, respectively.

  The R image light, G image light, and B image light emitted from the exit-side polarizing plates 8R, 8G, and 8B are incident on the dichroic cross prism 9. In the dichroic cross prism 9, the R image light is reflected by the red reflecting dichroic film 9R, the B image light is reflected by the blue reflecting dichroic film 9B, and the G image light is reflected by the red reflecting dichroic film 9R and the blue reflecting dichroic film 9B. , The R video light, the G video light, and the B video light are combined and emitted from the dichroic cross prism 9. The combined light of the R video light, the G video light, and the B video light is projected onto a screen (not shown) by the projection lens 10, and an enlarged color projection video screen is displayed on the screen.

  A heat sink 11 is provided behind each LED light source 1R, 1G, 1B. The heat sink 11 has the longest rectangular parallelepiped shape in the direction opposite to the emission direction of the emitted light, thereby reducing the thickness direction of the device without impairing the cooling effect, and reducing the thickness of the device. We are trying to make it. In addition, the heat sink 11 for R light is made larger than the heat sink 11 for G light or B light so that the LED light source 1R for R light which is weak against heat can be best cooled. Moreover, although the cooling fan 12 is used for every heat sink 11, the cooling effect is heightened, especially rotation of this cooling fan 12 so that the airflow of the cooling fan 12 for LED light source 1R which radiate | emits R light may become the maximum. Increase the number.

  FIG. 5 is a block diagram showing a second embodiment of the projection display apparatus according to the present invention. 3Gb ′ is a half-wave retardation plate, and parts corresponding to those in FIG. Therefore, duplicate explanations are omitted. Since the polarization conversion elements 3R and 3B in the second embodiment have the same configuration as the polarization conversion elements 3R and 3B in FIG. 1, the reference numerals of these parts are omitted.

  In the first embodiment shown in FIG. 1, the R, G, and B lights incident on the dichroic cross prism 9 are all converted from S-polarized light into image light corresponding to the image in the image light forming system. It is colored light. Thus, the R and B lights formed from the S-polarized light are efficiently reflected by the R light reflecting dichroic film 9R and the B light reflecting dichroic film 9B provided in a crossing manner in the dichroic cross prism 9. On the other hand, the G light formed from the S-polarized light is transmitted through the R light reflecting dichroic film 9R and the B light reflecting dichroic film 9B, but its transmission bandwidth is limited, thereby reducing the loss of G video light. Arise.

  This second embodiment reduces the loss of G video light in the dichroic cross prism 9 and uses G light of P-polarized light for this purpose.

  In FIG. 5, substantially parallel elliptically polarized G light emitted from the incident-side light pipe 2G enters the polarization conversion element 3G from the incident surface 3Gc. In this polarization conversion element 3G, the incident G light passes through the half-wave retardation plate 3Gb ′, and the P-polarized light of the elliptically polarized G light is transmitted through the polarization separation film 3Ga, and the S-polarized light is transmitted. By reflecting, it is separated into P-polarized light and S-polarized light. The P-polarized G light transmitted through the polarization separation film 3Ga is emitted from the emission surface 3fG to the emission-side light pipe 4G, and the S-polarized G light reflected by the polarization separation film 3Ga is emitted from the ½ wavelength phase difference plate 3Gb ′. The light is converted into S-polarized G light, further reflected by the reflective film 3Gd, and emitted from the emission surface 3fG to the emission side light pipe 4G.

  In the exit-side light pipe 5G, P-polarized G light is incident from the polarization conversion element 3G, and is emitted with a reduced cross-sectional size. The G light is incident on an image light forming system including an incident-side polarizing plate 6G that transmits only P-polarized light, a transmission-type image display element 7G, and an output-side polarizing plate 8G that transmits only P-polarized light. It is formed. The G image light is incident on the dichroic cross prism 9, passes through the R light reflecting dichroic film 9R and the B light reflecting dichroic film 9B, and is reflected by the R light reflecting dichroic film 9R and the B light reflecting dichroic film 9B. R video light and B video light are combined.

  In this way, by making the G image light incident on the dichroic cross prism 9 P-polarized light, attenuation in the R light reflecting dichroic film 9R and the B light reflecting dichroic film 9B can be reduced. The transmittance can be increased.

  Here, depending on the material used for the wavelength wave height source of the light emitted from the LED light source, the G light from the LED light source as shown in FIG. The spectral spectrum SPG is wide and its peak wavelength is 500 to 540 nm. On the other hand, the spectral spectrum SPB of the B light from the LED light source is narrower than that of the G light, but the peak wavelength is 450 to 490 nm, and the bands of the G light and B light are close to each other. Are overlapping.

  By the way, in the second embodiment using the LED light sources 1R, 1G, and 1B, the dichroic cut filter 5G having the characteristics of the bandpass filter is used to limit the band due to the shift of the spectral spectrum accompanying the temperature change. The G image light is incident on the dichroic cross prism 9 in a wide band and close to the B image light band.

Further, in the dichroic cross prism 9, in order to efficiently transmit the G video light in the wide band, as shown in FIG. 6, a part of the transmission region _GTME having a high transmittance of the G video light is partially converted into the B video light. so as to overlap with part of the reflection region B _REF of the high reflectance, the reflection region B _REF of the high reflectivity of the B image light, to set the transmission region G _TME high transmittance of G image light. The half-value wavelength λ _1/2 of the dichroic cut filters 5G and 5B is in a region where the reflection region B _REF and the transmission region _GTME overlap.

Here, the dichroic cut filter 5G and the dichroic cut filter 5B limit the band so that these bands do not overlap even if the spectral bands of the G video light and the B video light shift due to temperature changes. It has been added. Also in the dichroic cross prism 9, if the band of the spectrum spectrum of the G image light that has been band-limited by the dichroic cut filter 5 </ b> G is changed in temperature, it shifts due to the temperature change of the band of the spectrum spectrum of the adjacent B image light. possible to the reflection region B _REF, but shifted, as shown in FIG. 6, the transmission area G _TME high transmittance of the G image light is broadened to overlap a part of the reflection region B _REF, The spectral band of the G image light is not limited by the dichroic cross prism 9, and the G image light can be used efficiently.

It is a block diagram which shows 1st Embodiment of the projection type video display apparatus by this invention. It is a figure which shows the external appearance of the illumination optical system in FIG. It is a figure which shows the relationship between the shift by the temperature change of the spectral spectrum of colored light, and the half value wavelength of the dichroic cut filter in FIG. It is a figure explaining the setting value of the half value wavelength of the dichroic cut filter in FIG. It is a block diagram which shows 2nd Embodiment of the projection type video display apparatus by this invention. FIG. 6 is a diagram schematically illustrating a spectrum of R, G, and B light and a reflection region of R and B image light and a transmission region of G image light in the dichroic prism in FIG. 5.

Explanation of symbols

1R, 1G, 1B LED light source 2R, 2G, 2B Incident side light pipe 3R, 3G, 3B Polarization conversion element 3Ra, 3Ga, 3Ba Polarization conversion film 3Rb, 3Gb, Gb ′, 3Bb 1/2 wavelength retardation plate 3Rc, 3Gc , 3Bc Incident surface 3Rd, 3Gd, 3Bd Reflective film 3Re, 3Ge, 3Be Triangular prism 3Rf, 3Gf, 3Bf Emission surface 4R, 4G, 4B Emission side light pipe 5R, 5B, 5G Dichroic cut filter 6R, 6G, 6B Incident side Polarizing plate 7R, 7G, 7B Transmission type image display element 8 Output side polarizing plate 9 Dichroic prism 9R R light reflecting dichroic film 9B B light reflecting dichroic film 10 Projection lens 11 Heat sink 12 Cooling fan

Claims (14)

LED light source that emits light, an illumination optical system that converts light from the LED light source into predetermined polarized light, a video display element that emits the polarized light to generate video light, and emitted from the video display element In a projection-type image display device having projection means for projecting the image light to the screen,
A projection-type image display device comprising a dichroic cut filter that cuts a light component outside the predetermined band of the polarized light irradiated to the image display element. In claim 1,
A projection-type image display apparatus, wherein a difference between a half-value wavelength of the dichroic filter and a peak wavelength of light from the light source unit is approximately ½ of a bandwidth of the light. In claim 1,
The half-value wavelength λ _1/2 of the dichroic cut filter is
Assuming that the bandwidth of the light source is A (nm) and the peak wavelength is P (nm), the half-value wavelength n (nm) of the dichroic cut filter is set in the following range.
λ _P + W / 2-10 ≦ λ _1/2 ≦ λ _P + W / 2 + 10
Or
λ _P −W / 2−10 ≦ λ _1/2 ≦ λ _P −W / 2 + 10
Where λ _{P is} the peak wavelength of light
W: Projection-type image display device, characterized in that it has a bandwidth of a spectral spectrum of light. In claim 1,
The dichroic cut filter is an ultraviolet cut filter. In claim 1,
The dichroic cut filter has a half-wavelength set on the short wavelength side of the spectral band of the light, and cuts a shorter wavelength side than the half-value wavelength of the light. In claim 1,
The dichroic cut filter has a half-value wavelength set on the long wavelength side of the spectral spectrum band of the light, and cuts the longer wavelength side of the half-value wavelength of the light. In claim 1,
The dichroic cut filter has a half-value wavelength set on the short wavelength side and the long wavelength side of the spectral spectrum band of the light, and a wavelength shorter than the half-value wavelength on the short wavelength side of the light and the light. A projection-type image display device, characterized in that it is a band-pass filter that cuts light at a longer wavelength side than the half-value wavelength at the longer wavelength side. In claim 1,
In the dichroic cut filter, a half-value wavelength is set on the shift side of the spectral spectrum band of the light emitted from the LED light source depending on the temperature. In any one of Claims 1-8,
A projection-type image display device, wherein a heat sink having a substantially rectangular parallelepiped shape is provided on the side opposite to the light emitting side of the LED light source. First to third LED light sources that emit R (red) light, G (green) light, and B (blue) light, respectively, and R, G, and B light from the first to third LED light sources, respectively. First to third illumination optical systems for converting into predetermined linearly polarized light, and R, G, B light from each of the first to third illumination optical systems are irradiated, and R image light, G image light, Projection for projecting first to third image display elements for generating B image light, and projecting the R image light, G image light, and B image light from the first to third image display elements on a screen, respectively. In a projection-type image display device comprising means,
A projection-type image display device, wherein the first and third illumination optical systems are each provided with a reflecting element for changing the optical paths of the R light and the B light. In claim 10,
The projection type image display device, wherein the reflection element changes the optical path by approximately 90 °. In claim 10 or 11,
The direction of changing the optical path of the R light by the reflecting element of the first illumination optical system and the direction of polarization of the optical path of the B light by the reflecting element of the third illumination optical system are opposite to each other. Projection-type image display device. In claim 10, 11 or 12,
The first and third illumination optical systems respectively convert R and B light incident from the first and third LED light sources into S-polarized R and B light,
The second illumination optical system converts G light incident from the second LED light source into P-polarized G light, and a projection-type image display device. In claim 13,
A dichroic cross prism for combining the R video light, G video light, and video light from the first to third video display elements;
A projection-type image display device, wherein the transmission region of the dichroic prism capable of transmitting the G image light and the reflection region of the B image light can be partially overlapped.

Images